Ok thanks but I know of the create unit cheat and I don't think it works for non existent units. For example, you can't give the Germans cataphract cavalry. In the unit list file, there's barbarian onagers for the Dacian's and the Scythian's only,

type barb onager daciantype barb onager scythian

so I imagine typing either of these in for the Gaul's or Germans would have no effect.